What is your superior field (or CTV) border when treating para-aortic lymph nodes with extended field radiation therapy for endometrial cancer in the post-operative setting?

For women treated with IMRT, there are multiple ways to define the upper border of the field 1) contouring the PAs up to where the renal vessels exit the aorta 2) Treated up to vertebral body levels (i.e. T12/L1 or L1/2) 3) Treat to a certain distance (i.e. 3 cm) or vertebral body above a known positive lymph node How do you contour the CTV, do you use only one method, or alternate between them? Any benefits to one approach over another?